The main purpose of a foundation is to provide support for the entire structure. However the type of foundation depends on the structure of the soil one is to build on (Determined by a "Etude de Sol (G2)").

1. Screw Piles ("Pieux Visses"). They are galvanized metal pipes that are screwed down into the soil till it reaches a stable geological layer. They are often used in situations where the soil consists of clay. Their benefits are that they have a minimal carbon footprint and that they cause a minimal impact to the soil.

2. Concrete or brickwork piers. One needs to dig down till a stable geological layer has been reached. Applicable in cases where the stable soil is relatively close to the surface.

3. Footings and stem wall ("Vide Sanitaire"). In general this is a technique that is frequently used for new builds in the South West of France. One digs a trench to put the footing down and then a stem wall is build on top of the footings. This stem wall is about 60 cm above grade so that the ground floor does not touch the (humid) soil underneath. It also provides a crawl space for doing the occasional maintenance on pipes and cables. 

Posts will be attached to the foundation by means of steel connectors as depicted in the example on the left.